This invention relates to an electronic musical instrument capable of producing a musical tone by utilizing a frequency modulation system.
Various proposals have been made for producing a musical tone by an electronic musical instrument. These proposals include, for example, a system according to which a musical tone waveform for producing a certain tone colour is memorized in a memory and the waveform is successively read from the memory, a system according to which a desired tone colour is obtained by filtering a tone source waveform containing abundant harmonic components through a filter for attenuating some harmonic components, and a system according to which harmonics of respective orders are individually and separately produced and amplitude of each harmonic component is individually controlled to produce a desired tone colour. These prior art electronic musical instruments, however, have limitation in the scope of variation of the tone colour. It is particularly difficult in the prior art instruments to produce a musical tone which contains harmonic components of integer and non-integer orders at complicated ratios which varies with time.